Stationary starting winding switch for electrical motors

ABSTRACT

A stationary switch adapted principally for use in circuit with the starting winding of an electrical motor and normally adapted to be opened or closed by a rotary centrifugal speed-responsive actuator mounted on the shaft of the motor. A contact-carrying leaf spring is mounted on a base plate for engagement with a second contact carried by the base plate. The secured end of the leaf spring projects beyond the point of securement, and preferably beyond the margin of the base plate, and has an electroconductive arm in face-to-face abutment therewith from the terminal end to a point beyond the point of securement; the combined thickness of the leaf spring and the arm being such as to be frictionally secured to each other when engaged by a single slidable terminal connector, such as a spade connector. Tensor means for applying a predetermined stress or tension to the contact end of the leaf spring are provided by one of several alternative means, including the use of the arm to act as the tensor means. The arm also may serve as a stop to limit movement of the contact end of the leaf spring away from the other contact carried by the base plate.

United States Patent [191 Greenhut Nov. 25, 1975 [76] Inventor: Joseph Greenhut, 3333 Warrensville Center Road, Shaker Heights, Ohio {22] Filed: May 16, 1974 {21] Appl No.: 470,609

[52] US. CI 200/246; 200/250 [51] Int. Cl. H IIOIH 1/26 [581 Field of Search 200/283, 246, 250, 159 A, 200/80 R [56] References Cited UNITED STATES PATENTS 2,092,478 9/1937 Sommermayer 200/250 X 2,768,260 10/1956 Greenhut 200/80 R 3,177,311 4/1965 Torrico .i H 200/283 X 3,501,608 3/1970 Rulseh et a]. 200/283 3,588,392 6/1971 Cartwright 200/284 X 3,745,279 7/1973 Zollman i 200/80 R 3,790,730 2/1974 Wyland .i 200/80 R X 3,805,005 4/1974 Wilkinson 200/284 FOREIGN PATENTS OR APPLICATIONS 297,156 5/1954 Switzerland .1 200/283 Primary Examiner-lames R. Scott Assistant Examiner-William J. Smith Attorney, Agent, or FirrnIsler & Ornstcin [57] ABSTRACT A stationary switch adapted principally for use in circuit with the starting winding of an electrical motor and normally adapted to be opened or closed by a rotary centrifugal speed-responsive actuator mounted on the shaft of the motor. A contact-carrying leaf spring is mounted on a base plate for engagement with a sec ond contact carried by the base plate, The secured end of the leaf spring projects beyond the point of securement, and preferably beyond the margin of the base plate, and has an electroconductive arm in faceto-face abutment therewith from the terminal end to a point beyond the point of securement', the combined thickness of the leaf spring and the arm being such as to be frictionally secured to each other when engaged by a single slidable terminal connector, such as a spade connector, Tensor means for applying a predetermined stress or tension to the contact end of the leaf spring are provided by one of several alternative means, including the use of the arm to act as the tensor means, The arm also may serve as a stop to limit movement of the contact end of the leaf spring away from the other contact carried by the base plate.

13 Claims, 6 Drawing Figures US. Patent Nov. 25, 1975 3,922,514

STATIONARY STARTING WINDING SWITCH FOR ELECTRICAL MOTORS BACKGROUND OF THE INVENTION The use of starting winding switches for electrical motors, usually referred to as stationary switches, and used in combination with a suitable centrifugallyactuated. speed-responsive device mounted on the motor shaft, is known to the art. For a fuller description of these types of devices, reference is made to U.S. Pat. Nos. 2,616,682; 2,768,260 and 3,396,251. The stationary switches of the prior art commonly utilize a suitable support plate or base plate of non-conductive or dielectric material on which is secured at least one resilient electro-conductive leaf or arm carrying an electrical contact which is adapted to engage a second contact which is also provided on the base plate. A somewhat heavier rigid metallic arm, made of steel or the like, generally underlies the terminal end of the resilient leaf and projects beyond the end of the base plate. Both the steel piece and the resilient leaf have a common securement to the base plate by means of suitable fasteners, most commonly, hollow brass rivets. The thickness or gauge of the steel piece is approximately three to four times greater than the gauge of the resilient contact arm, and is sufficiently thick to be frictionally engaged by a terminal connector, such as the conventional spade connector, by means of which the leads are connected to the stationary switch. The resilient leaf spring is usually a thin reed of phosphor-bronze or beryliumcopper whose electro-conductivity is far superior to that of the steel terminal piece, which piece tends to introduce a significant value of electrical resistance into the circuit. This undesirable electrical resistance is further compounded by the fact that the electrical contact between the terminal end of the leaf or reed and its un' derlying steel terminal piece is essentially dependent upon the limited surface area of contact provided by the riveted securement and the degree of snugness of the rivets. The commonly used hollow rivets or eyelets also have a tendency to loosen over a period of time due to the constant movement of the reed, which may result in a severely diminished extent of electrical contact for the terminal end of the reed and may, eventually result in a complete loss of electrical contact.

In order to provide a pre-stressing or predetermined operating tension for the contact end of the resilient leaf, it has become customary to form the steel terminal piece with a transverse rib or other similar embossment which underlies and abuts the terminal end of the leaf to provide a fulcrum or bend-point which loads the leaf to a desired predetermined condition of stress or tension for operating purposes. The forming of the steel piece introduces an additional element of cost in the manufacuture of the stationary switch and, more significantly, does not permit of any variation or adjustment in such tension, unless it is accomplished by the forming of a separate run of steel pieces having a different height or configuration of tensor rib.

The invention herein described is directed to these problems encountered in prior art stationary switches.

SUMMARY OF THE INVENTION It is a primary object of the invention to provide a stationary switch structure having improved terminal electro-conductivity.

It is another object of the invention to provide a stationary switch having a secondary or supplementary form of securement which increases the electrical contact surface area between the terminal connector and the contact reed or leaf, as well as minimizing the possibility of loss of contact through loosening of the eyelets or rivets which are utilized for the primary securement.

Still another object of the invention is to provide improved and less costly tensor means for pre-loading or pre-stressing the resilient contact reedv BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of a stationary switch embodying the features of the invention.

FIG. 2 is an enlarged cross-sectional view, taken as indicated on line 2-2 of FIG. 1.

FIG. 3 is a fragmentary cross-sectional view similar to FIG. 2, but showing a modification of the invention.

FIG. 4 is an enlarged cross-sectional view, similar to FIG. 2, showing another modified form of the invention.

FIG. 5 is a fragmentary cross-sectional view, similar to FIG. 2, showing still another modified form of the invention.

FIG. 6 is a cross-sectional view, similar to FIG. 2, showing another modified form of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawings, there is shown a stationary switch structure, identified by the reference numeral 10, and utilizing a double pole switch arrangement. It will be understood that the switch arrangements can be single pole or multi-pole, depending upon requirements.

An insulating or dielectric support member or base plate 11 is provided for supporting the contacts and switch arms. The base plate is provided with a central opening 12 which serves as a clearance hole for the motor shaft (not shown) which extends therethrough when the switch 10 is mounted in position on the end bell or frame of the motor. Suitable mounting holes I3 are provided in the base plate for securing it in position on the motor. The base plate is herein illustrated as having a rectangular periphery or configuration, as this is its most commonly used form. However, it will be understood that the invention can be utilized with other configurations of support members or base plates and that the rectangular shape here shown is merely exemplary.

A pair of electro-conductive resilient reeds or leaf springs 14, each carrying an electrical contact 15 at one end thereof, are mounted on the base plate 11 in parallel spaced relationship on diametrically opposite sides of the central shaft opening 12. The other or terminal end 16 of the reed 14 projects from a recess 17 to a position beyond the marginal edge 18 of the base plate 11 and is secured to the plate by a hollow rivet or eyelet 19.

An electro-conductive arm 20, having a thickness approximately twice that of the reed I4, is disposed in overlying face-to-face abutment with the reed I4 extending from its terminal end to a point just beyond the securement provided by the eyelet I9. The eyelet is a securing means which is common to both the reed l4 and the arm 20. Thus, the arm 20 can be considered to be coextensive with the terminal end of the reed l4 and 3 the two pieces in combination provide a terminal tab or connector tab which can be slidably engaged by a terminal connector such as the commonly used spade connector which will serve to frictionally maintain the arm 20 and the portion 16 of the reed in tight electrical contact with each other and also will provide a supplementary seeurement of these two pieces to each other additional to the securement provided by the eyelet 19.

Mounted on a contact arm 21 is a contact 22 which underlies and is normally spaced from the contact 15. The contact arm 22 is desirably made of the same highly electro-conductive material as the leaf spring 14 and also has its terminal end 23 projecting beyond the margin 24 of the base plate 11. A connector arm 25, similiar to the previously described connector arm 20, is in face-to-face abutment with the contact arm 21 and extends coextensively therewith from its projecting end to its point of securement to the base plate, which is provided by an eyelet or rivet 26.

It will be noted that the recess 17 is provided with an upwardly directed slope or inclined surface 27 inboard of the securement 19. The recess 17 and its inclined surface 27 can be molded into the base plate 11 or can be machined or cut into the base plate, as desired. It will be apparent that the securement of the leaf spring 14 by the eyelet 19 on the flat or coplanar surface 28 of the recess creates a fulcrum effect at the upper edge of the slope 27 causing bending of the reed 14 to preload it or stress it so that it provides increased mechanical resistance to displacement during operation. The slope 27 thus serves as a tensor means for controlling the tension of the reed l4 and selectively establishing a desired deflection characteristic and travel characteristic in the reed. The angle of the inclined surface 27 and the spacing of that surface from the point of securement are variables which will affect the extent of preloading of the reed 14. After a proper location of the tensor means has been established for a particular switch operating condition, the recess 17 may be uniformly duplicated in production runs for the stationary switch. However, when the stationary switch is to be utilized for a somewhat different set of operating conditions which require a change in the pre-established tension on the reed 14, the disposition of the slope 27 in the recess 17 may be modified slightly to make proper adjustment in the tension of the reed 14, without the necessity of any change in the other components of the stationary switch.

it will be apparent by reference to the previously mentioned patents, that when the electrical motor is at rest, the centrifugal actuating device bears against the reeds l4 and deflects or displaces them into circuitclosing relationship between the contacts and 22. In order to avoid unnecessary wear on the reeds 14 by the rotary centrifugal device, it is customary to provide the reed 14 with a wear pad 29, as illustrated, against which the rubbing action of the rotary device is concentrated. When the motor is energized, the closed contacts 15 and 22 maintain the starting winding of the motor in the circuit until the motor approaches or attains its running speed, at which point the speed-responsive centrif ugal device retracts from engagement with the reeds, permitting the contacts to open to remove the starting winding from the circuit. As previously noted, the leads to the stationary switch are provided with slidable terminal connectors which frictionally engage the combined thickness of the arm and the abuting reed end 16 to secure them to each other in tight electrical contact. The end of the reed 14 is thus brought into direct electrical contact with the electrical leads to the switch without any of the intermediate electrical resistance introduced by the prior art form of steel connector tab previously described. Additionally, it will be noted that the electrical contact of the reed is not limited to the area of securement defined by the eyelet 19, but that a substantially greater surface area of contact of the reed 14 is involved, thus further minimizing the electrical resistance of the switch. Even if the eyelet 19 gradually becomes looser, the primary terminal contact area will still be fully effective so that failure of the switch will not result therefrom.

The improved tensor means provided by the sloped recess 17, not only eliminates the expense of an additional forming operation for a separate tensor element, but also provides a quick and inexpensive means for varying the tension on the reed during separate production runs of switches, as different applications or circumstances dictate.

in order to achieve consistent uniformity of result in the switching action, it is customary to use some sort of stop to limit the upward or withdrawal movement of the reed 14 so that its position will always be the same at the time that disengagement with the rotary device occurs. In FIG. 3 of the drawings, there is shown a mod ified form of the invention in which the previously described connector arm 25 is provided with a formed extension 30 to provide an insulation-surfaced stop lip 31 which is disposed in the path of upward or withdrawal movement of the contact end 15 of the reed 14 to establish a limiting position therefore. By utilizing the extension 30 the connector arm thus serves a dual purpose.

FlG. 4 of the drawing shows another modified form of stop arrangement for the reeds 14. This is provided by a substantially rigid extension 32 of the connector arm 20, the extension being bent upwardly to the desired degree to create an overlying stop for the body of the leaf spring 14. The degree to which the extension is bent determines the limit of upward movement of the leaf spring 14 and this can be adjusted as required.

In FIG. 5 of the drawings, a modified tensor arrangement is shown in which the connector arm 20 underlies the terminal end 16 of the reed and is provided with an extension 33 which is bent upwardly to a desired extent under the reed 14 to provide a fulcrum or tensor means for pre-tensioning of the leaf spring. The length of the extension 33 and the degree of its bend determine the pre-loading of the reed and provide for adjustment when necessary. When this form of tensor means is utilized, the stop arrangements of FIG. 3 can be utilized for the upper limit of withdrawal movement of the reed or some alternative form of stop arrangement can be used in lieu of the stop arrangement described with reference to FIG. 4.

FIG. 6 of the drawings shows a modified form of the connector arm arrangement shown in FIGS. 1 and 2 of the drawings, but utilizing a mounting arrangement for the contact arm 21 which permits so-called overrun of the reed 14 after it engages the contact 22, without introducing a significant or sudden reaction force on the reed. This arrangement also permits the heighth of the reeds 14 and the contact arms 21 above the top surface of the base plate 1! to be reduced significantly, thus permitting use of the stationary switch in motors where the close longitudinal dimension might other wise require use of some other, less desirable, form of switch. The base plate 11 is provided with a recessed portion 34 which, as in the embodiment of FIG. 1, serves as a point of securement for the terminal end I6 of the reed l4 and the connector arm 20. A molded rib 35 is provided on the surface of the base plate 11 inboard of the recess 34 to serve as a tensor means for the reed 14. For any particular application, the heighth and distance inboard of the rib will establish the pre-tensioning of the reed. A molded stop member 36 is provided on the upper surface of the base plate II in overlying relationship to the contact end 15 of the reed and serves to limit the withdrawal movement of the reed from circuit-making position. The marginal end 37 of the stop member 36 serves as a bridge overlying a recess 38 which is coplanar with the body of the base plate 11 and extends inboard of the margin of the base plate to intersect an opening 39 under the stop memher.

The contact arm 21 and its associated connector arm is secured to the underside of the portion 37, as by eyelet 19, in a position so that the contact 22 projects into the area of the opening 39 in underlying relationship to the contact 15 and to the molded stop 36. When the contact end 15 of the reed is deflected by the rotary device into circuit-making engagement with the contact 22, the resilient contact arm 2] does not bottom on the surface of the base plate 11 as in the previously described embodiments, but is yieldably displaced by the contact 15 so as not to establish any significant reaction force against the reed 14 or its associated speed-responsive actuator which could cause nonuniformity of operation of the switch. This arrangement also permits mounting of the contact arm 21 in the plane of the base plate 11 to reduce the required height of the stop member 36, as well as reducing the limit of upward movement of the reed 14 above the surface of the base plate. It will be apparent that when the thickness of the base plate 11 is sufficient, the previously described opening 39 can take the form of a cavity or recess which will provide sufficient clearance for the downward movement of the contact 22 below the upper surface of the base plate. It will also be apparent that in the various forms of the invention described herein, the contacts 15 and 22 could be disposed so as to be midway on the base plate or at some other convenient point on the base plate, rather than being adjacent one or the other margin of the base plate, as illustrated in the drawings. Under such circumstances, where the contact arm 21 may be considerably longer than illustrated in the drawings, it may be desirable to also provide a stop to limit the upward position of the contact arm 21 and, for this purpose, the connector arm 25 may be provided with an extension 32 to act as a stop, just as such extension 32 was previously described as a stop for the reed 14 in FIG. 4.

It is to be understood that the forms of my invention, herewith shown and described, are to be taken as preferred examples of the same, and that various changes in the shape, size and arrangement of parts may be resorted to, without departing from the spirit of my invention, or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. In a starting winding switch for an electrical motor, the combination of a dielectric base plate, an electroconductive leaf spring secured to said base plate adjacent one end thereof and having said one end projecting beyond said securement, an electrical contact provided on the other end of said spring and yieldably urged to a switching position relatively to a second contact provided on said base plate, an electro-conductive arm of different material than the spring having at least twice the thickness of the spring secured to said leaf spring and extending in face-to-face abutment coextensively therewith from said one end to at least said securement, said securement being a fastener traversing said spring and arm and base plate, and said spring and arm at said one end being frictionally engageable by a slidable terminal connector to mechanically secure them in electrical contact with each other at a point spaced from and independent of said first-named securement.

2. A combination as defined in claim 1, including tensor means associated with said spring to establish a pre selected tension for said other end thereof.

3. A combination as defined in claim 1, wherein said one end of said leaf spring projects beyond the margin of said base plate.

4. A combination as defined in claim I, wherein said arm underlies said leaf spring.

5. A combination as defined in claim 2, wherein said tensor means is a deformation of predetermined angularity in said arm in abutment with said spring.

6. A combination as defined in claim 1, wherein said arm overlies said spring.

7. A combination as defined in claim 6, wherein said arm limits movement of said other end of said spring away from said second contact.

8. A combination as defined in claim 2, wherein said base plate is provided with a recess for receiving said leaf spring and said arm at said first-named securement, and said tensor means is an edge of said recess inboard from said first-named securement in underlying abutment with said leaf spring.

9. A combination as defined in claim 1, including a second electro-conductive leaf spring secured to said base plate adjacent one end thereof and having its said one end projecting beyond its securement, the other end of said second spring carrying said second contact, a second electro-conductive arm of different material than the spring having at least twice the thickness of the spring secured to said second leaf spring and extending in face-to-face abutment therewith from its said one end to at least its point of securement, said second spring and second arm at said one end being frictionally engageable by a slidable terminal connector to mechanically provide an additional securement therefor spaced from and independent of their first-named securement.

10. A combination as defined in claim 9, wherein said second arm overlies said other end of said first leaf spring to limit movement thereof away from said second contact.

11. A combination as defined in claim 9, wherein said base plate is provided with a recess for receiving said other end of said second leaf spring and is provided with a cavity underlying said second contact.

12. A combination as defined in claim 9, wherein said second arm overlies said second spring to limit the upward extent of movement thereof.

13. A combination as defined in claim 9, including a cavity provided on said base plate in underlying relationship to the contact end of said second arm to provide a clearance space for downward deflection thereof relatively to said base plate. 

1. In a starting winding switch for an electrical motor, the combination of a dielectric base plate, an electro-conductive leaf spring secured to said base plate adjacent one end thereof and having said one end projecting beyond said securement, an electrical contact provided on the other end of said spring and yieldably urged to a switching position relatively to a second contact provided on said base plate, an electro-conductive arm of different material than the spring having at least twice the thickness of the spring secured to said leaf spring and extending in face-to-face abutment coextensively therewith from said one end to at least said securement, said securement being a fastener traversing said spring and arm and base plate, and said spring and arm at said one end being frictionally engageable by a slidable terminal connector to mechanically secure them in electrical contact with each other at a point spaced from and independent of said first-named securement.
 2. A combination as defined in claim 1, including tensor means associated with said spring to establish a pre-selected tension for said other end thereof.
 3. A combination as defined in claim 1, wherein said one end of said leaf spring projects beyond the margin of said base plate.
 4. A combination as defined in claim 1, wherein said arm underlies said leaf spring.
 5. A combination as defined in claim 2, wherein said tensor means is a deformation of predetermined angularity in said arm in abutment with said spring.
 6. A combination as defined in claim 1, wherein said arm overlies said spring.
 7. A combination as defined in claim 6, wherein said arm limits movement of said other end of said spring away from said second contact.
 8. A combination as defined in claim 2, wherein said base plate is provided with a recess for receiving said leaf spring and said arm at said first-named securement, and said tensor means is an edge of said recess inboard from said first-named securement in underlying abutment with said leaf spring.
 9. A combination as defined in claim 1, including a second electro-conductive leaf spring secured to said base plate adjacent one end thereof and having its said one end projecting beyond its securement, the other end of said second spring carrying said second contact, a second electro-conductive arm of different material than the spring having at least twice the thickness of the spring secured to said second leaf spring and extending in face-to-face abutment therewith from its said one end to at least its point of securement, said second spring and second arm at said one end being frictionally engageable by a slidable terminal connector to mechanically provide an additional securement therefor spaced from and independent of their first-named securement.
 10. A combination as defined in claim 9, wherein said second arm overlies said other end of said first leaf spring to limit movement thereof away from said second contact.
 11. A combination as defined in claim 9, wherein said base plate is provided with a recess for receiving said other end of said second leaf spring and is provided with a cavity underlying said second contact.
 12. A combination as defined in claim 9, wherein said second arm overlies said second spring to limit the upward extent of movement thereof.
 13. A combination as defined in claim 9, including a cavity provided on said base plate in underlying relationship to the contact end of said second arm to provide a clearance space for downward deflection thereof relatively to said base plate. 